Tube support in motional x-ray irradiation apparatuses



June 9, 1959 HuszAR 2,890,349

TUBE SUPPORT IN MOTIONAL X-RAY IRRADIATiON APPARATUSES Filed Aug. 30, 1952 I 4 Sheets-Sheet l INVEN TOR. 4452i 0 16 6/5248 L. HUSZAR June 9, 1959 TUBE SUPPORT IN MOTIONAL x-RAY IRRADIATION APPARATUSES 4 Sheets-Sheet 2 Filed Aug. 50, 1952 INVENTOR. z 14524 0 #05244 mfk.

June 9, 1959 HuszAR 2,890,349

TUBE SUPPORT IN MOTIONAL X-RAY IRRADIATIQN APPARATUSES Filed Aug. 30, 1952 4 Sheets-Sheet 3 VINVENTOR. F 11 Y 445210 #052 419 June 9, 1959 L. HUSZAR 2,890,349

TUBE SUPPORT IN MOTIONAL X-RAY IRRADIATION APPARATUSES Filed Aug. 30, 1952 4 Sheets-Sheet 4 74 INVENTOR.

TUBE SUPPORT IN MGTIONAL X-RAY IRRADIATION APPARATUSES Laszlo Huszar, Budapest, Hungary, assigior to Licencia Talalmanyokat Ertekesito Vallalat, Budapest, Hungary, a firm Application August 30, 1952, Serial No. 307,209 Claims priority, application Hungary September 4, 1951 10 Claims. (Cl. 250-91) This invention refers to improvements in and relating to a tube support for motional X-ray irradiation apparatus.

The latest development in X-ray therapy aims at improving -the so-called motional irradiation treatment in which thetumour to be dissolved is exposed to a moving X-ray beam. The main significance of this sort of treatment is that the tumour receives a high dose of irradiation while the adjacent sound portions of the patients body and above all the area of his or her skin through which the -X-ray beam enters, i.e. the ports of entry, are substantially relieved from exposure, since the X-ray beam, which is constantly directed towards the tumour, continuously changes its position and thereby successively traverses different portions of skin and body.

Several methods for performing X-ray irradiation in the above described manner have heretofore been developed. There is the rotation treatment wherein the patient sits on a motor driven rotating stool while a stationary horizontal X-ray beam is always directed towards the centre of the tumour. Another method with similar effect is swinging pendulum irradiation. In this case the patient lies on a special treatment couch while the X-ray tube swings at a fixed angle round an axis passing through the tumour. The angle is normally set from to 180 but may in suitable cases be set up to 360. Both the rotation treatment and the swinging pendulum irradiation have the common drawback that the X-ray beam traverses the patients body in a single plane which is perpendicular to the axis of rotation and oscillation, respectively, causing the sound body portions surrounding the tumour to receive a considerable amount of irradiation, since the X-ray beam is divergent and in the successive positions thereof the irradiated areas intersect one another. In order to eliminate this drawback it has been suggested to cause the X-ray tube focus to describe a spiral movement on the surface of a spherical sector, the X-ray beam of small dimensions always being directed on to the same point, the centre of the convergent and rotating beam. This results in a conical beam, the apex of which lies just under the tumour growth. The process itself is called the convergent beam irradiating method. Although in this case the dose distribution is most favourable, the convergent beam irradiation method is still affected with a serious drawback in that the aperture angle ofthe conical beam and thereby the area of ports of entry is limited by the ratio of focalor target-skin distance to tumour-skin distance in a plane which goes through the longitudinal aXis of the patients body. Obviously, above a certain value of the aperture angle of the conical. beam the said ratio rapidly alters in such a way that the depth dose is more and more absorbed before reaching the tumour whilst the skin dose is increasing to detrimental values. E.g., assume that the focal-skin distance amounts to 50 cm. and the tumour lies in a depth of cm. in a normal plane which is perp'endicular to the longitudinal axis of a cylindrical body and, consequently, to the skin surface. If the X-ray atent beam now falls in a slant plane which encloses with the normal plane an angle of 45, the tumour-skin distance increases by 50% whereas the skin dose is about higher relative to the values in the normal plane. Obviously, such shifting of the irradiation characteristics is inadmissible and, therefore, the aperture angle of the conical beam is limited to substantially lesser values than 2 4S=90. However, also a limitation of the area of the ports of entry is entailed thereby which, in turn, restricts the ratio of depth dose to skin dose and finally the absolute value of the depth dose itself.

The present invention aims at eliminating the drawbacks of the above mentioned methods of motional irradiation and of further improving the ratio of depth dose to skin dose, respectively, by a suitably formed tube support. It is based upon the discovery that the ports of entry and thereby the ratio of depth dose to skin dose can be increased greatly if the tube holder performs a composed motion wherein it travels around the longitudinal axis of the patients body and, at the same time, makes use of the scope of slant irradiation which is still admissible as regards absorption within the body and increase of dose upon the skin surface. Accordingly, the present invention refers to a tube support in motional X-ray irradiation apparatus comprising a tube holder and consists in providing drive means for moving said tube holder around two axes perpendicular to and intersecting each other.

Further details of the present invention will be described with reference to the accompanying drawings which show, by way of example, the principle and embodiments thereof. In the drawings:

Fig. 1 is a perspective view showing the principle of supporting and moving the tube holder.

Fig. 2 is a top view to Fig. 1.

Figs. 3 to 6 are perspective views showing the surface struck by a single X-ray where the tube holder is moved in accordance with the present invention.

Figs. 7 and 8 are diagrammatic views showing the areas of dose concentration at different ratios of motions around the two axes.

Fig. 9 is an elevational view of one embodiment of the invention.

Fig. 10 is an elevational view showing a portion of a further embodiment.

Fig. 11 is a diagrammatic view showing the self-intersection of an X-ray beam with rectangular cross section at the turning points of an angular path of the tube holder.

Fig. 12 is a sectional view taken along line X-X of Fig. 10, showing a detail.

Fig. 13 is a perspective view of another embodiment of the invention.

Fig. 14 is an elevational view of a portion of a still further embodiment.

Similar parts of construction are referred to by the same numbers of reference throughout the drawings.

Referring to the drawings, in Fig. 1 reference numeral 15 denotes the body of a patient to be treated by X-ray irradiation. For sake of simplicity the body is supposed and referred to as being cylindrical. The tumour to be dissolved in body cylinder 15 is designated by nun ber of reference 16. It is supposed to lie in the longitudinal axis 17 of body cylinder 15. In order to obtain a high concentration of irradiation in the area of tumour 16 without over excitation of the neighbouring sound body portions, a tube holder 18 is, in accordance with the main feature of the present invention, moved around two axes perpendicular to and intersecting each other so as to direct an X-ray 19 into the center of tumour 16 3 through continuously changing ports of entry. One of said rotation axes is formed by longitudinal axis 17 of body cylinder 15 whereas the other one is constituted by axis 20 which goes through tumour 16 thus intersecting axis 17, both axes 17 and 20 enclosing a right angle. Moving around axis 17 tube holder 18 describes a circular path 21 of radius 22 with tumour 16 as centre whereby X-ray 19 strikes the surface of circle 21. Moving around axis 20 tube holder 18, on the other hand, describes a curved path 23 of radius 22 also with tumour 16 as centre whereby X-ray 19 strikes the surface of a sector the boundaries of which are constituted by curved path 23 and by radius 22 in its two extreme positions associated with the ends of path 23. Obviously, if both movements take place, X-ray 19 moves within a hollow spherical body which is bordered by a spherical calotte and two right cones with their apices in tumour 16 as it is clear from the drawing, the base circles of said cones being indicated by dotted lines 25 and 26. During this motion X-ray 19 continuously changes its position, its point, however, is constantly directed towards tumour 16. Thus, tumour 16 is constantly exposed to irradiation whereas the ports of entry continuously change so that the sound portions of body cylinder 15 encircling tumour 16 as well as the body surfaces serving as ports of entry receive but a fraction of the depth dose.

Obviously, instead of rotating tube holder 18 around axis 20 it is also possible to oscillate it along path 23 as it is suggested by double arrow 27. In this case, tube holder 18 passes path 23 several times in alternate directions during one complete revolution thereof around axis 17, e.g. in direction of arrow 28. This composed motion can be carried out by shifting tube holder 18 along path 23 without rotation around axis 17, then forwarding it around axis 17 while resting at one end of path 23. Thereafter, tube holder 18 is moved back along path 23 into its other extreme position at constant angular position as regards axis 17, whereupon another partial rotation around axis 17 takes place, and so on. Thus, tube holder 18 describes a meander-like path 29 as shown in Fig. 2, the arrow points therein indicating the direction of the successive movements of tube holder 18. At the same time X-ray 19 strikes a fan-like surface composed of right cones of rectangular cross section, as shown in Fig. 3. However, both motions can also take place simultaneously, in which case the fan-like surface struck by X-ray 19 shows a form illustrated in Fig. 4.

Depending on the size of angular displacement around axis 17 between two successive alternate movements around axis 20 or on the ratio of angular velocities around axes 17 and 20, respectively, the folds of the fan-like configuration follow one another frequently, as shown in Figs. 3 and 4, or are spaced substantially, as illustrated in Figs. and 6. This difference has its significance not only in the possibility of regulating the amount of the depth dose during a complete revolution around axis 17 without altering the emission of the X- ray tube, but also in that the concentration of the irradiation to a certain area around tumour 16 is rendered possible thereby. Figs. 7 and 8 show this in two extreme cases. In case of Fig. 7 tube holder 18 performs a number of transverse motions around axis 20 during a complete revolution thereof around axis 17. Since instead of a single X-ray 19, which has been chosen for explaining the theoretical principles of the invention, practically there is an X-ray beam 30 directed towards tumour 16, beams 30 partly overlap one another as tube holder 18 performs its successive transverse motions around axis 20. Thus, a series of adjacent spheres of different depth doses (isodoses) are formed around tumour 16 the irradiation amounts of which consecutively decrease towards the periphery. There is a relatively large middle sphere with highest concentration of irradiation which is surrounded by several layers of increasing thickness and decreasing concentration as it is indicated in Fig. 7 by a corresponding density of hatching.

In contradistinction to this, in case of Fig. 8 tube holder 18 performs but four transverse motions or oscillations around axis 20 during one complete revolution thereof around axis 17. Obviously, the overlappings of beams 30 are practically negligible, so that a single sphere of highly concentrated depth dose results only, without the adjacent portions of body cylinder 15 being exposed to substantial irradiation.

Obviously, by altering the ratio of angular speeds around axis 17 and axis 20, respectively, an adjustment of the range and concentration of irradiation is rendered possible, which is of great importance as regards X-ray therapy. There are tumours, e.g. Bronchial-Ca, which cannot sharply be limited so that an irradiation of the body portions adjacent to the tumour proper seems advisable. In such cases the irradiation may be carried out as described with reference to Fig. 7. Sharply distinguishable tumours, e.g. Oesophagus-Ca., on the other hand, may be handled according to the performance described in connection with Fig. 8.

An X-ray apparatus embodying the tube support in accordance with the present invention is illustrated in Fig. 9. Tube holder 18 is movably arranged on a curved guide means 23 formed by a toothed are along which tube holder 18 can be oscillated by means of a gear motor 31 in any usual manner. Reference numeral 32 denotes a socket for the terminal plug of a not represented cable by which gear motor 31 can be connected to a suitable source of current. Curved guide means 23 is attached to an arm 33 fulcrumed at 34 to a column 35. The proportions of guide means 23, arm 33 and fulcrum 34 are selected so that axis 17 of fulcrum 34 is perpendicular to and intersecting axis 20 of curvature of guide means 23. Fulcrum 34 is connected to another gear motor 36 supported by a bracket 37 of column 35. Socket 38 of gear motor 36 serves for applying a suitable voltage thereto by means of a cable not represented in the drawing. Another column 39 supports a treatment couch or stretcher 40 the lateral position and level of which is rendered adjustable by means of a hand wheel 41 and a pedal 42, respectively, in a manner Well known in the art.

In operation, a patient 15 is laid upon stretcher 40 and the latter is-by means of hand wheel 41 and pedal 42adjusted so that tumour 16 to be irradiated within the chest of patient 15 lie exactly in the point of intersection of axes 17 and 20, as indicated by double arrows 43 and 44. The depth dose to be delivered being predetermined, a suitable X-ray tube 45 with a tube head 46 is fixed on tube holder 18 and both gear motors 31 and 36 are set into motion. The angular speeds of oscillation around axis 20 and of rotation around axis 17 are selected so as to produce an irradiation of desired amount and concentration exactly in the desired area of the patients body 15.

Guide means 23 may be provided with control means for automatically reversing gear motor 31 in the extreme positions of tube holder 18. Such means are-by way of example-illustrated in Fig. 10. Gear motor 31 is provided on its either side with a press-button switch 47 which-in extreme positions of tube holder 18strikes against an abutment 48 fixed to guide means 23.

Since X-ray beam 30 is usually of rectangular cross section, as indicated at 49 in Fig. 10, moving tube holder 18 along a meander-like path, as shown e.g. in Figs. 3 and 5, causes overlapping 50 of the irradiated fields, as illustrated in Fig. 11. Such an overlapping or self-intersection of the ports of entry might increase the surface dose to disturbing values. In order to avoid such unfavourable etfects the apparatus may-in accordance with a further feature of the inventionbe provided with screen means adapted to protrude in the path of X-ray beam 30 in extreme positions of oscillation of tube holder 18. Such screen means are demonstrated in Figs. 10

and 12. The base portion of abutments 48 is extended so as to form a bracket 51 which has a further bracket 52 fixed to it. Bracket 52 forms a dovetailed guide for a slide 53 the upper surface of which is covered by a layer 54 of lead forming the screen means proper. The mutual position of slide 53 and dovetailed guide 52 is rendered adjustable by means of a wing-headed screw 55. In extreme positions of tube holder 18, lead layer 54 engages 'with slots 56 in tube head 46, thereby interrupting the path of X-ray beam 30, as shown in Fig. 12. Thus, overlapping 50 are suppressed and distubing overdoses on the surface eliminated.

Screw 55 serves for adjusting lead layer 54 in accordance with the angle of oscillation of tube holder 18 so as to cause screen means 54 to protrude to a predetermined extent across the path of X-ray beam 30 in extreme positions of oscillation of tube holder 18. A corresponding adjustment of reversing switches 47 is rendered possible by a dovetailed guide 57 formed integral with abutment 48 for receiving non represented additional abutments which, when inserted, suitably shorten the oscillation stroke of tube holder 18. Obviously, any other suitable means well known in the art might be employed as well.

Fig. 13 represents a further embodiment of the invention. While the embodiment shown in Fig. 9 Was of the single column type, this apparatus is formed as a wall-supported device. The main diflference between the two embodiments consists in that rotation of tube holder 18 around axis 17 is rendered possible by a stationary angular support 21 in which a ring-shaped guide means 58 supporting curved guide means 23 is rotatably arranged. One of the side surfaces of guide means 58 is provided with a toothed rim 59 which cams with a pinion 60 of gear motor 36. The latter is fixed to a bracket 61 of stationary support 21 which is-'by means of rods 62suspended on the ceiling 63 of a room. Patient 15 is supported by a usual stretcher 40, the front legs 64 of which have previously been raised through the opening of ring-shaped guide means 58. The distance between front legs 64 and rear legs 65 of stretcher 40 permits suitable shiftings which may be needed for adjustments in the horizontal plane.

As it is known in X-ray therapy, the focal-skin distance will preferably be altered for each treatment of the same patient. To this purpose, the radial length of arm 33 of the apparatus shown in Fig. 9 may be adjustable. A corresponding adjustment of the radius of guide means 23 might be rendered possible by providing a set thereof the members of which are interchangeable and have a different curvature. According to the latter, each guide means is associated with another radius, or, as regards Fig. 9, with another arm length of rotation around axis 17. In case of Fig. 13, the radius of rotation around axis 17 might be altered by e.g. forming the above mentioned interchangeable guide means each with a support of different radial length. By such an arrangement the associated radii are fixed by one and the same guide means member so that the use of schedules or adjustings of further machine parts may be dispensed with.

Fig. 14 shows that instead, of a curved guide means 21, a straight guide means 66 might also be applied. In this case the oscillating motion of tube holder 13 along path 23 is composed by an alternate straight lined motion of a sliding carriage 67, and by an angular motion of tube holder 18 proper. To this purpose, tube holder 18 is pivotally connected to carriage 67 by a pivot 68 which is supported by a bearing 69. The rear side of tube holder 18 is formed as a "toothed are 70 which cams with a pinion 71 driven by gear motor 31 in any suitable manner, preferably by the same axle which causes carriage 67 to slide along straight guide means 66. Obviously, when carriage 67 performs its alternate motion along straight guide means 66, as indicated by double arrow 72, tube holder 18 oscillates around pivot 68 in directions of double arrow 73. The proportions are selected so that the longitudinal axis 74 of tube holder 18 is always directed towards the tumour, whereby also the X-ray beam is directed thereto.

The embodiments of the invention are shown with a separate motor for each motion, whereby an individual regulation thereof is possible within wide ranges. However, by using a suitable mechanic chain, e.g. a Bowden wire in case of Fig. 9 and a friction drive gear in case of Fig. 13, a second motor might be dispensed with. By inserting variable speed gears in the drive mechanisms for rotation and oscillation, respectively, the ratio of angular velocities can suitably be altered in spite of using a single motor only.

The angular displacement of tube holder 18 around axis 17 of rotation and axis 20 of oscillations, respectively, can be varied between 0 to 360 and 0 to about 60, respectively, as it is necessitated by the special conditions of an X-ray treatment. The whole process of rotation and oscillation can be rendered entirely automatic by means well known in the art and, therefore, neither described, nor illustrated in its details. The same applies to the construction and working conditionsvoltages, cooling, etc.of the X-ray tube which is of the usual type and well known to those skilled in the art.

What I claim is:

1. Supporting and guiding means for the tube holder of movable X-ray apparatus, comprising an oscillation guide along which the tube holder may oscillate, means supporting said oscillation guide adjacent its mid-portion for rotation about a single circle having an axis generally parallel with the longitudinal axis of the oscillation guide, and including the point of support of the oscillation guide and means for effecting the aforesaid oscillation and rotation whereby the tube holder describes a predetermined regular meandering path substantially an equal distance on either side of and across the aforesaid circle of rotation, while maintaining said tube holder constantly aimed at a preselected target located at a point on the aforesaid axis of rotation.

2. Supporting and guiding means for the tube holder of movable X-ray apparatus, comprising an oscillation guide along which the tube holder may oscillate, means supporting said oscillation guide adjacent its mid-portion for rotation about a single circle having an axis generally parallel with the longitudinal axis of the oscillation guide and. including the point of support of the oscillation guide, means supporting a target for X-ray irradiation at the center of the circle of rotation of said oscillation guide support, and means for effecting the aforesaid oscillation and rotation simultaneously whereby the tube holder describes a meandering predetermined regular path substantially an equal distance on either side of the aforesaid circle of rotation and rotates completely around the aforesaid target while maintaining the tube holder in a position constantly directed at the target.

3. Supporting and guiding means for the tube holder of movable X-ray apparatus comprising an arcuate oscillation guide along which the tube holder may oscillate, means supporting said oscillation guide adjacent its midportion for rotation about an axis generally parallel with the longitudinal axis of the oscillation guide, the radius of curvature of the oscillation guide and the radius of the circle of rotation being substantially equal, and means for effecting the aforesaid oscillation and rotation simultaneously whereby the tube holder describes a meandering path substantially an equal distance on either side of the equator of a sphere having as its center the center of curvature of the oscillation guide and the center of the circle of rotation.

4. Supporting and guiding means for the tube holder of movable X-ray apparatus, comprising an oscillation guide along which the tube holder may oscillate while constantly pointing toward a first axis, means supporting said oscillation guide adjacent its mid-portion for rotation about a single circle including the point of support of the oscillation guide and having a second axis, and means for effecting said oscillation and rotation, whereby the tube holder oscillates on either side of the aforesaid circle of rotation, the arrangement of the foregoing being such that both the said first axis and the said second axis are perpendicular to and intersecting with each other and with a third axis representing the axial center line of said tube holder in the medial position of its oscillating motion.

5. Supporting and guiding means for the tube holder of movable X-ray apparatus, comprising an arcuate oscillation guide along which the tube holder may oscillate, an arm pivotally supported in a stationary support and supporting said arcuate guide adjacent its mid-portion for rotation about an axis generally parallel with the longitudinal axis of the oscillation guide, the radius of curvature of the oscillation guide and the radius of the circle of rotation being substantially equal, and drive means for eifecting the aforesaid oscillation and rotation simultaneously whereby the tube holder describes a meandering path on either side of the equator of a sphere having as its center the center of curvature of the oscillation guide and the center of the circle of rotation.

6. Supporting and guiding means for the tube holder of movable X-ray apparatus, comprising an arcuate oscillation guide along which the tube holder may oscillate, a ring shaped guide rotatably mounted in a stationary support, said ring shaped guide adjacent its mid-portion supporting said oscillation guide for rotation about an axis generally parallel with the longitudinal axis of the oscillation guide, the radius of curvature of the oscilla tion guide and the radius of the ring shaped guide being substantially equal, and drive means for effecting the aforesaid oscillation and rotation whereby the tube holder describes a meandering path on either side of the ring shaped guide.

7. Supporting and guiding means for the tube holder of movable X-ray apparatus, comprising a straight guide means, a sliding carriage arranged on said straight guide means, a tube holder having an opening for the passage of rays pivotally arranged on said sliding carriage, rotational guide means supporting said straight guide means adjacent its center portion, and drive means for oscillatively moving said sliding carriage along said straight guide means and pivoting said tube holder around said pivot in a manner to maintain the opening pointed toward the center of rotation of the rotational guide means, and means for rotating said straight guide means around the axis of said rotational guide means whereby the tube holder describes a meandering path lying on a cylinder having as its center the center of rotation and as its equator the circle of rotation of the rotational guide means.

8. Supporting and guiding means for the tube holder of movable X-ray apparatus, comprising an oscillation guide along which the tube holder may oscillate While constantly pointing toward a first axis, means supporting said oscillation guide adjacent its mid-portion for rotation about a single circle including the point of support of the oscillation guide and having a second axis, means for eiiecting said oscillation and rotation whereby the tube oscillates on either side of the aforesaid circle of rotation, the arrangements of the foregoing being such that both the said first axis and the said second axis are perpendicular to and intersecting with each other and with a third axis representing the axial center line of said tube holder in the medial position of its oscillating motion, and screen means disposed to protrude in the path of the X-ray beam in extreme positions of oscillation of said tube holder.

9. In an apparatus for radiation therapy, a source of radiation, means for rotating said source in a vertical circle about a horizontal axis, means for directing a beam of radiation from said source at a point on said horizontal axis and means for moving said source in a direction perpendicular to the plane of said vertical circle, said beam being directed at said point at each position of the source. I

10. In an apparatus for radiation therapy, a source of radiation, means for rotating said source in a vertical circle about a horizontal axis, means for directing a beam,

of radiation from said source at a point on said horizontal axis, and means for moving said source through an arc centered at said point and extending in a direction perpendicular to the plane of said vertical circle, said beam being directed at said point at each position of the source.

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